1. Field of the Invention
The present invention pertains to a solenoid driver system, and more specifically, a solenoid driver system for energizing a solenoid coil with a rapid rise output signal that energizes the solenoid coil for rapid turn on and reduces the time lag between a turn on signal and the actual energizing of the coil.
2. Description of the Prior Art
The prior art control of solenoids has been concerned with reducing solenoid power requirements while still providing an ample holding voltage for the solenoid. Prior art solenoids have utilized a dropping resistor across the solenoid coil which resulted in wasted power being converted into heat. Further, the driving signal was a decreasing signal of a waveform characterized as a downward curved ramped signal. The heat that the solenoid coil or coils would add to the surrounding environment was sometimes sufficient such as to raise the temperature in an existing environment.
Prior art did not appear to have recognized the requirement for rapid turn on of the solenoid coil with accuracy followed by minimum lower holding current, such as through pulse width variation thereby minimizing heat buildup and dissipation in the solenoid coil.
As multiple solenoids were added, the response and holding voltage degraded resulting in a slower opening and less adhesive pressure.
Representative prior art patents include U.S. Pat. No. 4,630,165, entitled "DC Power Control for DC Solenoid Actuators", and U.S. Pat. No. 3,864,608, entitled "Combination Mono Stable and A Stable Inductor Driver".
The particular application for the present invention is for a glue gun applicator, requiring accurate turn on of the solenoid. In the prior art devices, the solenoid control would tend to burn out the solenoids or the turn on time was not accurate. In the past, the glue gun was left on all of the time, or in the alternative, a pulse was used to turn on a solid state relay that was synchronized to the AC line. Based on a 60-cycle AC line and the point of the cycle, the inaccuracy of previous dispensing methods of solenoid control could be as much as 8 milliseconds between high and low peaks, depending on where the control pulse was applied in reference to the AC line which is completely asynchronous. This resulted in sporadic glue dispensing and solenoid control.
The present invention overcomes the disadvantages of the prior art by providing control of a solenoid with low power where the modulating circuit and the trigger circuit maintain the coil power to a reasonably low value, and there are no AC synchronization problems. This provides that the use of the solenoid coil becomes accurate and economical. When the present invention is applied to glue dispensing, accuracy is extremely enhanced in providing a consistent application of glue, and minimizing or eliminating waste of the glue.